The NFL suffered a stunning blow Thursday when an arbitrator ruled that there is enough evidence in the grievance case of former San Francisco 49ers quarterback Colin Kaepernick to send it to a full hearing.

Arbitrator Stephen Burbank denied the NFL’s request for summary judgment and a dismissal of the case, an eye-opening ruling that allows Kaepernick’s collusion grievance against the league to continue. Burbank now will hold a full hearing, possibly before the end of the year, and issue a final ruling.

Kaepernick has been a polarizing figure since he began protesting social injustices by kneeling during the national anthem two years ago. Kaepernick’s representatives, led by celebrity attorney Mark Geragos, filed a suit against the league in October, contending that NFL teams and their owners have conspired to keep him from working in the league since he left the 49ers on March 2, 2017.

49ers cornerback Richard Sherman said last year he knows why Kaepernick is still unemployed. “What is it about?” he said. “It’s not about football or color. It’s about, ‘Boy, stay in your place.’ ”

Burbank’s ruling now puts the image-conscious NFL under a bigger, more public microscope. NFL owners, coaches and executives will face more intense questioning and cross-examinations in the trial-like setting of a full arbitrator’s hearing than they did in depositions.

Some of the league’s heavy hitters already have been deposed in the case: Commissioner Roger Goodell, Dallas Cowboys owner Jerry Jones, New England Patriots owner Robert Kraft, Seattle Seahawks coach Pete Carroll and general manager John Schneider, and Baltimore Ravens coach John Harbaugh were all questioned with Kaepernick present.

Before a gag order was issued in the case, Goodell denied there was a concerted effort to keep Kaepernick sidelined. “Those are football decisions that each team has to make and what they think are the right ways to make their football teams better,” Goodell said.

In arguing to dismiss the case, the NFL contended that Kaepernick’s attorneys had not met the burden of proof stipulated by the collective bargaining agreement between the league and its players association.

The arbitrator’s ruling did not surprise Stanford law professor William Gould, but he said it does indicate Kaepernick has a substantial case. “You would anticipate that given the fact that there have been many depositions taken that there would be issues of fact here, which could possibly allow Kaepernick to prevail,” Gould said.

Gould added that Kaepernick’s legal team still faces real hurdles at the full hearing. “He will have to most likely through trial-like proceedings meet his burden, which is to show through a preponderance of evidence that collusion exists,” Gould said. “And it’s a tough burden in a case like this because the agreement explicitly says you can’t rely simply upon the fact that other players with dissimilar qualifications were picked by clubs for the vacancies that were available.

“We know that Jay Cutler was chosen by Miami,” he added. “He was booed out of Chicago. Surely Kaepernick was preferable to him, and I think that’s the case, but that alone will not carry the day for Kaepernick.”

Kaepernick, aside from holding Know Your Rights camps for inner-city youths, has maintained a low profile. When approached May 8 by this news organization following a workout with Reid at Cal State East Bay in Hayward, Kaepernick said: “We’re not doing interviews. We’re just here getting in a workout.”

Kaepernick won 28 of 58 games as the 49ers starter, first seizing that role during the 2012 season en route to a berth in Super Bowl XLVII, where the 49ers fell to the Ravens. He was 4-2 in playoff action.